Optical couplers are commonly used to combine and/or separate light signals with a particular class of couplers referred to as wavelength division multiplexers (WDMs). WDMs combine and/or separate the light signals based on wavelength. WDM-type couplers may also be used to measure the wavelength of the light signal based on the coupler's inherent wavelength dependence. Knowing the wavelength of the light signal may be important in many applications.
For example, in fiber optic gyroscope (FOG) applications, knowing the wavelength of the light signal traveling through the sensing coil is important for determining a scale factor of the FOG. The scale factor describes the capability of the FOG to accurately sense angular velocity at different angular rates. Thus, the scale factor of the FOG describes the sensitivity of the sensor.
Unfortunately, the optical coupler's ability to measure a light signal's wavelength may be impacted by variations of refractive index and coupler length due to the environmental variations. Therefore, it would be beneficial to fabricate an optical coupler that is relatively insensitive to these variations.